The long-term goal of the Data Core is to develop and maintain a mechanism to support the computer, data processing, experimental design and data analysis needs for investigators engaged in the long-term study of Alzheimer Disease and other dementias. Research projects falter for many reasons. One reason is the failure to focus sufficient attention on the often times tedious process of monitoring the acquisition and handling of information. Valid conclusions are virtually impossible when based upon unreliable or faulty data. Considerable care is necessary in attending to the details of complete data collection, data movement, verification, storage and processing as well as details of experimental design and analysis. We have developed a mechanism to collect, transfer and process data from diverse sites in such a way as to maximize its reliability and timely processing while minimizing the problems introduce by data missing as a result of inappropriate or careless collection or processing. We have also taken care to insure its long-term safety. Considerable effort has been allocated to the goal of processing of complete and reliable information. We have developed a close interaction with other cores and projects of the OADC by maintaining daily contact and participating in their activities. We have also provided biostatistical support to investigators for data analysis projects, peer-reviewed publications and applications for extramural funding as well as training for staff to biostatistics. Importantly, we have taken care to allow for the expansion of our support to new investigators and projects in an orderly and coherent manner.